Supports for pre-stressing strands in concrete construction



Oct. 15, 1963 R. M. MCROBBIE 0 SUPPORTS FOR PRE-STRESSING STRANDS IN CONCRETE CONSTRUCTION Filed Aug. 9, 1960 INVENTOR. Robert M. Mc Robbie diiorr ag United States Patent 3,106,803 SUPPQRTS FUR PRE-STRESSING STRANDS EN CUNCRETE CGNSTRUCTIUN Robert M. McRohbie, New York, N.Y., assignor to Richmond Screw Anchor Company, inc, New York, N.Y., a corporation of New York Filed Aug. 9, 1960, Ser. No. 48,373 1 Claim. (Cl. 50-130) This invention relates to devices for use in connection with the concrete casting of pre-stressed beams, girders, or other elements or structures.

It is an object of the invention to provide a device of this character which will efiectively hold the pre-stressing strands in their properly draped positions during the casting of the beams, girders, or other elements.

It is an object of the invention to provide a device in which rotatable elements such as rollers are eliminated; which device provides means by which the spacing between the engaged strands can be readily varied, both from the bottom of the form and also from one another; which can also be constructed that lateral spacing of the strands can be arranged as required for particular uses, and which has various other uses and advantages as will be apparent to those skilled in this art.

More particularly, the invention contemplates the provision of an adjustable frame of box-like formation, the same consisting of a pair of flat plates having their edges connected by a plurality of strand-supporting saddles, each of the saddles including a hook-shaped terminal portion having an upper curved or arcuate surface on which the pre-stressing strand is rested. Provided within the frame is a threaded element, such as a coil of spirally- Wound metallic rod forming a nut for threadable engagement with a threaded rod or bolt on which the frame is thus threadably adjustable.

With these and other objects to be hereinafter set forth in view, I have devised the arrangement of parts to be described and more particularly pointed out in the claim appended hereto.

In the accompanying drawing, wherein an illustrative embodiment of the invention is disclosed,

FIG. 1 is a side elevational view of the strand holder constructed according to the invention;

FIG. 2 is a front elevational view of the same;

FIG. 3 is a sectional view, taken substantially on the line 3-3 of FIG. 1, looking in the direction of the arrows;

FIG. 4 is a detail view showing the helical coil and its mounting between the plates of the frame, and

FIG. 5 is a perspective view of one of the strandreceiving saddles.

Referring to the drawing, the numerals 1 and 2 indicate a pair of similar, spaced-apart, parallel metallic plates constituting side walls of a frame, and between which is fixed, by welding or other means, a spiral coil or helix 3, preferably but not necessarily, composed of round metallic rod. Said helix constitutes a threaded element or nut through which a threaded rod, bolt or other similar threaded element 4 is longitudinally or axially adjustable, or reversely, on which the frame is threadably adjustable.

The threaded rod, bolt or other threaded element 4 extends from the form or from other parts, and by threadable adjustment of the frame of which the plates 1 and 2 form the side walls, said frame may be suitably positioned to hold the stressed strands 5 and 6 (FIG. 2) in the desired draped or undulated positions through the form. The plates 1 and 2 are slotted as shown at 7 to facilitate the secure welding of the helical coil 3 between them.

Secured to the edges of the plates 1 and 2 by being welded thereto at suitably spaced positions, are the strandsupporting saddles 8. Each of said saddles is in the form of a plate having a terminal portion of substantially hook formation, the saddle consisting of a base portion 9 welded to the edges of the plates, and the upturned lower end 10 in the form of a hook, the upper surface 11 thereof being curved or arc-uately shaped, which surface serves as a curved seat for the strand 5, 6, which can slidably adjust itself on said seat when being stressed and draped.

The saddles 8 are securely welded to the edges of the spaced plates 1 and 2, thus maintaining the plates in properly spaced relation and co-operating with the plates in forming a rectangular, box-like frame within which the coil or helix is located at one end.

By threadable adjustment of the frame just described, along the length of the rod or other threaded element 4, the strands 5 and 6 will be properly draped in the form in the required spaced relation preparatory to the casting operation, and maintained in the required positions.

In the embodiment illustrated in the drawing, only two pairs of the saddles 8 are disclosed. The saddles in each pair are preferably, but not necessarily, arranged transversely opposite to one another, but in actual practice, possibly four or more pairs of the saddles will be used, the frame of which they form' a part being, in such case, of substantially greater length than that illustrated.

By the desired spaced positioning of the saddles on the frame, the relative spacing of the strands 5 and 6 can be regulated. Also, by increasing the width of the plates 1 and 2, the lateral spacing of the saddles, and hence the lateral positioning of the strands, can also be regulated.

The device is of sturdy construction; it is easily fitted in position and adjusted to secure the desired draping of the strands, and it utilizes no movable parts such as rollers, in its construction.

Having thus described a single embodiment of the invention, it is obvious that the same is not to be restricted thereto but is broad enough to cover all structures coming within the scope of the annexed claim.

What I claim is:

A support for the strands in pre-stressed concrete construction comprising, a rectangular frame including a pair of flat plates disposed in spaced-apart parallel relation, a spiral helix disposed between and secured to the plates, the edges of the plates being connected by cross-plates, the cross-plates being secured to said edges and being arranged in pairs and forming sides for the frame, the pairs of cross-plates being arranged in spaced relation along the length of the frame, each of the cross plates having a projecting hook-shaped strand support, each strand support having a curved, strand engaging surface extending crosswisely of the support.

References Cited in the file of this patent UNITED STATES PATENTS 2,175,555 Brown Oct. 10, 1939 2,364,628 Garlinghouse Dec. 12, 1944 2,880,949 Fuss Apr. 7, 1959 3,013,322 Oarr Dec. 19, 1961 OTHER REFERENCES Concrete, a publication, September 1957, page 60.

Hold Down Anchors for Pretensioned Prestressed Concrete, a publication by Superior Concrete Accessories, 'Inc., New York, N.Y., dated Dec. 2, 1957, received in Pat. 0. Div. 15, Apr. 3, 1959 (-a copy in Div. 33), hereafter referred to as Superior.

Construction Methods and Equipment, a publication, May 1958, pp. 102-104, a copy in Div. 15. 

